The present application is directed to a leak detection system and method, in particular a system and method for detecting rapid leaks such as those occurring when an automobile wheel tire gets a puncture. The rapid detection of punctures is generally of a critical nature, in particular on the motorway.
The detection system and method may be implemented by onboard computers, more specifically in a tire pressure monitoring system (TPMS) module. A TPMS module collects pressure information (P) and temperature information (T) concerning a gas contained in a tire with the aid of sensors and a radio-transmitter, which are generally fixedly attached to the wheel rim. A radio receiver disposed in the module permits a frame of data representative of the pressure and the temperature to be periodically received.
The period of acquiring measurement data frames from each wheel is in principle the inverse of the theoretical transmission frequency of frames by the transmitters which is determined by the onboard computer as a function of an operating state of the vehicle (stopped, running).
To detect a leak, its rate is calculated from the pressure change from one frame to another, at the above-mentioned theoretical frequency, i.e., the rate is calculated from the pressure variation registered over the theoretical time. However, this detection is not optimal since the temperature of the wheel rim, thus of the gas contained in the tire, can vary greatly during vehicle use, for example during braking. This temperature variation causes a variation in the pressure, thus in the calculated rate, which can be erroneously interpreted as a leak, causing false alarms.
Thermal compensation may be used to reduce the effect of the temperature variation. However, thermal compensation, even if it is applied, is not immediately reflected, given the long response time of a temperature sensor, longer than that of a pressure sensor. This problem is further exacerbated by the time between at least two frames which is not constant because 1) it may be voluntarily decreased, for example if the monitoring of the tire pressure needs to be increased, in which case the calculated rate decreases with the time between two frames, or 2) it may increase automatically if a frame is lost due to a poor radio link. The calculated rate can thus easily double.
Owing to its critical nature, a rapid leak such as a puncture must be detected as quickly as possible, which excludes the use of filtering techniques even though the precision of the sensors used would prompt such a use.
This is the reason why it is generally preferred to use methods solely based on the differential analysis of pressure variations (or rates) of the set of tires, or at least of those of the wheels of each of the axle systems of the vehicle, which has the advantage of obviating the use of temperature sensors, of initial tire pressures (at ignition) and of the use of filtering. However false alarms, mentioned above, remain possible.
Accordingly, there is a need for a solution to obviate as much as possible this risk of false alarms.